1. Field of the Invention
The present invention relates to a multipurpose engine in which a fuel gas evaporated within a fuel tank is adsorbed by an adsorbing material and the fuel gas separated from the adsorbing material is sucked into an intake system of the engine.
2. Description of Related Art
A conventional multipurpose engine with a canister disclosed in Japanese Unexamined Patent Application, First Publication No. 2005-163690 accommodates an adsorbing material which adsorbs the fuel gas evaporated within a fuel tank. The multipurpose engine with a canister includes a canister which adsorbs the fuel gas which leaks out from around a cap of the fuel tank, and returns the fuel gas to an intake system, and piping which takes the fuel gas into the canister is opened near an oil supply port of the fuel tank. This piping is coupled to the canister through the bottom of the tank from the inside of the fuel tank, and the fuel gas is charged and guided into the intake system through this piping. It is an aim of the prior art to shorten the piping for recovered fuel gas and to simplify attachment thereof to the intake system.
A conventional multipurpose engine disclosed in Japanese Unexamined Patent Application, First Publication No. H07-34985 includes an adsorption means which adsorbs the fuel gas evaporated within a fuel tank. As the multipurpose engine, a structure in which an adsorbing material is accommodated in a chamber (equivalent to a canister) formed in a lid for a fuel filling port of a fuel tank, the fuel gas separated through a gas-liquid separation chamber is made to be adsorbed by an adsorbing material within an adsorbing material chamber, and the degassed fuel gas is sucked into an intake system pipe by using the intake negative pressure of the engine is suggested. In addition, a structure in which a block of an adsorbing material is adjacent to the downstream section of a filter element of an air cleaner, and the fuel gas separated through a gas-liquid separation chamber from a fuel tank is directly delivered to the adsorbing material block, and the fuel gas is adsorbed by the adsorbing material, thereby performing degassing of the fuel gas is suggested.
When the fuel within the fuel tank is consumed by the operation of the engine, the pressure inside the fuel tank becomes negative, and thereby the fuel supply to the intake system is not smoothly performed. In the conventional multipurpose engine with a canister disclosed in the above 2005-163690, a liquid check valve which is adapted to keep a liquid fuel from leaking even if ambient air can be introduced into a fuel supplying cap of the tank, and through which gas can pass is provided. Further, the tip of the piping which feeds the fuel gas into, for example, the intake system is opened to an attachment portion of the cap, and this piping passes through a tank wall via the inside of the tank. Thus, a leak-preventing sealing means is provided between the piping and the wall. As a result, the structure is complicated, the cost is high, and the maintenance is not easy, either.
In the conventional multipurpose engine disclosed in the above 07-34985 having the adsorption devices, a valve body of a float valve through which liquid is checked, and gas can pass is fixed to an attachment opening of the cap. Further, the cap with which the canister is integrated is large. Therefore, the layout of parts in an engine is not simple, and the fuel supply operation can not be smoothly performed. On the other hand, in a case where the adsorbing material is provided adjacent to the filter element of the air cleaner, the introduction resistance of sucked air may become large, and may have influence on engine output.
The object of the invention is to solve these problems, and provide a multipurpose engine including a fuel gas adsorption device, which is simple and inexpensive in construction, and is easy to maintain.